| Ink-jet printing ink is one of the important factors which affect digital printing. Ink-jet printing ink usually comprises pigment, water, organic solvent, and some additives. At present, factories often use dye ink in digital printing. However, this method has a lot of disadvantages. Such as complex technology, using more water and discharging more waste-water. Also dye ink can't be used to all kinds of fibers. Compared with dye ink, pigment ink has so many advantages. First of all, pigment can be used to all kinds of fibers. It needs small space, has simple technology, can be big or small batch freely, is the same with personality consume using intent, has no waster of dye and additive, has no waster-water. Digital printing of pigment ink is friendly to the environment.In this paper, the principle of piezoelectric DOD digital inkjet printing was introduced. Also there were discussed how to prepare water-based ultra-fine pigment dispersions and how to judge the properties of the dispersions. The relationship between viscosity, surface tension, anti-foaming and deforming of the dispersions and its jetting property was analyzed. We made high viscosity and low viscosity dispersions, measured the density, viscosity, particle size and surface tension of the dispersions. Two ways were used to treat the high viscosity dispersion: a) high-speed shearing, 9000rpm, and 15min, b) ultrasonic treatment, 1000w, and 10min. Then we measured the viscosity change of the dispersion. Using jetting properties visualizer, we researched jetting properties. At last we analyzed the relationship between viscosity, surface tension, viscosity change after treatment by high-speed shearing and ultrasonic and jetting properties of high viscosity dispersions. Using Mimaki Jv4-180 machine, we measured the ink-jet properties of low viscosity dispersions. It was recorded by scrip. Three kinds of polyol were used to discuss the affection of polyol to the ink-jetting properties.For high viscosity dispersions, the result showed that, the ink-jetting property is determined by the viscosity and surface tension of pigment ink. If the dispersion had good ink jet properties, it must have good anti-foaming and de-foaming properties. If the dispersion had good anti-foaming and de-foaming properties, it not always had good ink-jetting properties. The variation of viscosity after ultrasonic treatment could reflect the ink-jetting property.For low viscosity dispersions, the particle sizes changed a little after the dispersions were treated 24h at 70℃.Glycerin, diethylene glycol, 1,2-Propylene glycol can be added to the water-based ultra-fine pigment dispersions. When the dosage of Glycerin, diethylene glycol, 1,2-Propylene glycol was 10% or 15%(w/w), the dispersions needed short leach time, had nice ink-jetting properties. Also the surface tension was reduced a little with the increase of dosage of the three kinds of polyol; it had nothing to with the ink-jetting properties.
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